Legionella: warmer weather, greater risk?

The effects of climate change continue to hit the headlines as we move into our fourth month of above average temperatures, with predictions of an Indian summer being reported.

Warm weather and hot summer holidays, quite naturally, see an increased use of many water applications. Air conditioning units and associated cooling towers, for example, are in greater demand in the summer, swimming pools are visited more frequently, and hose pipes are pulled out of hibernation for a summer of use.

While many are enjoying the warmest summer for many years, duty holders and responsible persons must be aware of the heightened – and hidden – risk of Legionella in water sources and systems.

To be able to flourish, Legionella needs a temperature range from 20-45°C – so the warmer weather is creating an ideal environment for the bacteria to grow and multiply. Temperatures in the UK this year have gone above and beyond 30°C, providing Legionella bacteria with warmer water systems to grow in.

Holiday parks, summer camps and public gardens

The seasonality of holiday parks, caravanning sites and summer camps mean they are typically used less frequently throughout winter months. Because of these quieter periods, stored and stagnant water can become a breeding ground for Legionella bacteria, especially when temperatures start to rise.

The risk of Legionella extends to any hot and cold water system and cooling tower as well as irrigation systems and interactive water features in public spaces which – in warmer weather – attracts the public. Guidance on the legislation around interactive water features can be found here.

Ground maintenance in public spaces, parks and grounds also require careful consideration. Like any other water accessory, dispenser or system, hose pipes can store stagnant water and therefore Legionella bacteria has the potential to grow. When next used, these hose pipes have the potential to release the airborne bacteria in tiny water droplets for inhalation, posing a risk to the user and anyone nearby.

Similarly, the same considerations and control measures must be applied to schools, universities and accommodations that are empty during the summer. Lack of use during the summer months significantly increases the Legionella risk once they become occupied.

Compliance all year round

Taking steps to keeping your water systems safe should be done in line with a Legionella risk assessment. It’s not just advisory; if you are an employer or in control of premises, you are responsible for understanding the health risks of Legionella. Failure to risk assess water systems for Legionella is punishable by fine and a prison sentence. More often than not, when outbreaks occur, there is a serious risk to human health often resulting in fatalities.

Control measures for safer water systems

With hotter weather often seeing an increased risk of Legionella proliferation, there are a number of precautions to take to ensure that you minimise the risk of cases of Legionnaires’ disease, ensuring that you are compliant with HSE’s ACoP L8.

For hot and cold water systems, controlling the temperatures to ensure the water is outside of the Legionella growth band is vital. Keep all hot water systems at above 60°C, with water outlets maintained at a minimum of 50°C; in healthcare environments, this should be 55°C. Likewise, cold water should be kept below 20°C, wherever possible. That is not to say that Legionella is not a risk in the winter months, but water below 20oC will mean the Legionella bacteria are dormant.

Water outlets that are infrequently used should be flushed regularly to avoid stagnation. Evaluating the usage of the water systems – in the Legionella risk assessment and ongoing following the risk assessment – will determine how regularly the outlet should be flushed. As a guide, any outlet that has not been used for a week or longer should be flushed for at least 3 minutes.

Even more effective, reducing the amount of water stored will limit the stagnation of the water and reduce the potential for the growth of Legionella bacteria. If this is not possible, flushing or draining all systems will reduce the risk – and should be outlined as a control measure in the risk assessment.

Where temperatures are scorching, air conditioning units and evaporative cooling towers are used frequently. Having appropriate control measures in place can prevent potential outbreaks from Legionella; chemical dosing, water treatment, sampling and regular maintenance can ensure water systems are safe to operate and use.

Adequate training

Ensuring staff are appropriately trained in Legionella awareness, risk assessment and their responsibilities can support in effective Legionella management and control. Not only that, suitable and sufficient training of all staff involved in Legionella risk management is a key requirement of the regulations.

If you require support in managing Legionella, conducting your Legionella risk assessments or want general advice on what to do, please get in touch by calling 0845 603 2112.